In the automotive industry, it is frequently necessary to know the pneumatic or hydraulic pressure in a container or along a pressure line. Current technologies for pressure measurement sensors include piezoresistive technology implemented using thick film, thin film and MEMS, which involve, for example, building a strain gage on the top surface of a sensing membrane.
Additionally, it is known to employ capacitive technology, for example on MEMS and/or discrete membranes, as seen by reference to U.S. Pat. No. 5,656,780 entitled CAPACITIVE PRESSURE TRANSDUCER WITH AN INTEGRALLY FORMED FRONT HOUSING AND FLEXIBLE DIAPHRAGM issued to Park (“Park”). Park discloses a pressure transducer that includes a reference capacitor electrode and a variable capacitor electrode, both of which are electrically connected to a circuit. The variable capacitor electrode and a conductive surface of a diaphragm form a variable capacitor whose capacitance varies with changes in a fluid pressure in a transducer chamber. The design disclosed in Park, however, is rather complicated and includes an increased number of parts. Generally, the conventional art of capacitive sensing requires elaborate manufacturing processes and an increased number of parts to assemble the sensing element. Moreover, these sensors also have a shortcoming insofar as not being able to effectively seal high pressures. In addition, conventional sensing membranes are generally not compatible with a wide range of media (i.e., the fluid whose pressure is being sensed).
There is therefore a need for a sensor that minimizes or eliminates the shortcomings as set forth above.